Method for producing aromatic hydrocarbons

ABSTRACT

Disclosed is a method for producing aromatic hydrocarbons including a cracking reforming reaction step of bringing a feedstock having a 10 vol % distillation temperature of 140° C. or higher and a 90 vol % distillation temperature of 380° C. or lower, into contact with a catalyst for monocyclic aromatic hydrocarbon production containing a crystalline aluminosilicate to cause the feedstock to react with the catalyst, and thereby obtaining a product including monocyclic aromatic hydrocarbons having 6 to 8 carbon numbers and a heavy oil fraction having 9 or more carbon numbers; a step of separating the monocyclic aromatic hydrocarbons and the heavy oil fraction from the product obtained from the cracking reforming reaction step; a step of purifying the monocyclic aromatic hydrocarbons separated in the separating step, and collecting the hydrocarbons; and a step of separating naphthalene compounds from the heavy oil fraction separated in the separating step, and collecting the naphthalene compounds.

TECHNICAL FIELD

The present invention relates to a method for producing aromatichydrocarbons.

Priority is claimed on Japanese Patent Application No. 2010-205903,filed Sep. 14, 2010, the content of which is incorporated herein byreference.

BACKGROUND ART

Light cycle oil (hereinafter, referred to as “LCO”), which is a crackedlight oil produced by a fluid catalytic cracking (hereinafter, referredto as “FCC”) units, contains a large amount of polycyclic aromatichydrocarbons and has been utilized as light oil or heavy oil. However,in recent years, investigations have been conducted to obtain, from LCO,monocyclic aromatic hydrocarbons having 6 to 8 carbon numbers (forexample, benzene, toluene, xylene, ethylbenzene and the like), which canbe utilized as high octane value gasoline base materials orpetrochemical feedstocks and have a high added value.

For example, Patent Documents 1 to 3 suggest methods for producingmonocyclic aromatic hydrocarbons from polycyclic aromatic hydrocarbonsthat are contained in LCO and the like in a large amount, by using azeolite catalyst.

PRIOR ART DOCUMENTS Patent Document

-   [Patent Document 1] Japanese Unexamined Patent Application, First    Publication No. H03-2128-   [Patent Document 2] Japanese Unexamined Patent Application, First    Publication No. H03-52993-   [Patent Document 3] Japanese Unexamined Patent Application, First    Publication No. H03-26791

DISCLOSURE OF INVENTION Technical Problem

However, in regard to the methods described in Patent Documents 1 to 3,it cannot be said that the yield of monocyclic aromatic hydrocarbonshaving 6 to 8 carbon numbers is sufficiently high.

Furthermore, in recent years, new effective utilization of LCO isanticipated. Specifically, in addition to efficient production ofmonocyclic aromatic hydrocarbons having 6 to 8 carbon numbers, such asbenzene, toluene, xylene and ethylbenzene, it is expected to produceother chemical products as effective by-products, by the same process oronly by adding a new process to part of the process.

The invention was achieved in view of the circumstances described above,and it is an object of the invention to provide a method for producingaromatic hydrocarbons, by which monocyclic aromatic hydrocarbons having6 to 8 carbon numbers can be produced in high yields from a feedstockcontaining polycyclic aromatic hydrocarbons, and also, other chemicalproducts, for example, aromatic hydrocarbons other than the monocyclicaromatic hydrocarbons, can be produced.

Solution to Problem

The present inventors conducted thorough investigations in order toachieve the object described above, and as a result, they obtained thefollowing findings.

Since LCO contains a large amount of polycyclic aromatic hydrocarbons,if this is subjected to a cracking reforming reaction treatment, arelatively large amount of a heavy oil fraction having 9 or more carbonnumbers can also be obtained in addition to the monocyclic aromatichydrocarbons having 6 to 8 carbon numbers. In regard to this heavy oilfraction, an investigation has been conducted to merely find that theheavy oil fraction may be collected as a light oil/kerosene basematerial, or may be recycled as a feedstock of the monocyclic aromatichydrocarbons.

Thus, the present inventors analyzed in detail the components of theheavy oil fraction in order to promote effective utilization of theheavy oil fraction, and as a result, the inventors found that the heavyoil fraction contains a large proportion of naphthalene oralkylnaphthalenes. Further, based on such findings, the inventorsfurther conducted investigations regarding the production of naphthaleneas a chemical product, in parallel to the production of the monocyclicaromatic hydrocarbons, and as a result, the inventors achieved theinvention.

That is, the method for producing aromatic hydrocarbons of the inventionincludes:

a cracking reforming reaction step of bringing a feedstock having a 10vol % distillation temperature of 140° C. or higher and a 90 vol %distillation temperature of 380° C. or lower, into contact with acatalyst for monocyclic aromatic hydrocarbon production containing acrystalline aluminosilicate to cause the feedstock to react with thecatalyst, and thereby obtaining a product including monocyclic aromatichydrocarbons having 6 to 8 carbon numbers and a heavy oil fractionhaving 9 or more carbon numbers;

a separation step of respectively separating the monocyclic aromatichydrocarbons having 6 to 8 carbon numbers and the heavy oil fractionhaving 9 or more carbon numbers from the product obtained from thecracking reforming reaction step;

a purification and collecting step of purifying the monocyclic aromatichydrocarbons having 6 to 8 carbon numbers thus separated in theseparation step, and collecting the monocyclic aromatic hydrocarbonshaving 6 to 8 carbon numbers; and

a naphthalene collecting step of separating naphthalene compounds thatinclude at least naphthalene, from the heavy oil fraction having 9 ormore carbon numbers thus separated in the separation step, andcollecting the naphthalene compounds.

Furthermore, in regard to the method for producing aromatichydrocarbons, the naphthalene collection step is preferably a step ofseparating and collecting methylnaphthalene and/or dimethylnaphthalene,and naphthalene.

Furthermore, the method for producing aromatic hydrocarbons preferablyincludes:

a hydrogenation reaction step of hydrogenating the fraction remainingafter naphthalene compounds have been separated in the naphthalenecollecting step and obtaining a hydrogenation reaction product; and

a recycling step of recycling the hydrogenation reaction product to thecracking reforming reaction step.

Also, in regard to the method for producing aromatic hydrocarbons, theapparatus for separating and collecting naphthalene compounds includingnaphthalene in the naphthalene collecting step is preferably adistillation apparatus.

Furthermore, in regard to the method for producing aromatichydrocarbons, it is preferable that the crystalline aluminosilicatecontain, as main components, a zeolite with medium-sized pores and/or azeolite with large-sized pores.

Furthermore, in regard to the method for producing aromatichydrocarbons, it is preferable to set the reaction temperature employedwhen the feedstock and the catalyst for monocyclic aromatic hydrocarbonproduction in the cracking reforming reaction step, to a temperatureranging from 400° C. to 650° C.

Also, in regard to the method for producing aromatic hydrocarbons, it ispreferable to set the reaction pressure employed when the feedstock andthe catalyst for monocyclic aromatic hydrocarbon production in thecracking reforming reaction step, to a pressure ranging from 0.1 MPaG to1.5 MPaG.

Furthermore, in regard to the method for producing aromatichydrocarbons, it is preferable to set the contact time for bringing thefeedstock into contact with the catalyst for monocyclic aromatichydrocarbon production in the cracking reforming reaction step, to aperiod ranging from 1 to 300 seconds.

Advantageous Effects of Invention

According to the method for producing aromatic hydrocarbons of theinvention, monocyclic aromatic hydrocarbons having 6 to 8 carbon numberscan be produced with a relatively high yield from a feedstock includingpolycyclic aromatic hydrocarbons, and in addition, naphthalene compoundsincluding naphthalene can be produced as other chemical products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining an embodiment of the method forproducing aromatic hydrocarbons of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the method for producing aromatic hydrocarbons of theinvention will be described in detail.

FIG. 1 is a diagram for explaining an embodiment of the method forproducing aromatic hydrocarbons of the invention, and the method forproducing aromatic hydrocarbons of the present embodiment is a methodfor producing monocyclic aromatic hydrocarbons having 6 to 8 carbonnumbers from a feedstock, and also producing naphthalene compoundsincluding naphthalene.

That is, the method for producing aromatic hydrocarbons of the presentembodiment preferably includes, as shown in FIG. 1:

(a) a cracking reforming reaction step of bringing a feedstock intocontact with a catalyst for monocyclic aromatic hydrocarbon productionto cause the feedstock to react with the catalyst, and obtaining aproduct including monocyclic aromatic hydrocarbons having 6 to 8 carbonnumbers and a heavy oil fraction having 9 or more carbon numbers;

(b) a separation step of separating the product produced in the crackingreforming reaction step into plural fractions;

(c) a hydrogen collecting step of collecting hydrogen that is producedas a by-product in the cracking reforming reaction step from the gascomponents separated in the separation step;

(d) an LPG collecting step of collecting LPG that is produced as aby-product in the cracking reforming reaction step from a liquidfraction separated in the separation step;

(e) a purification and collection step of purifying and collectingmonocyclic aromatic hydrocarbons from a liquid fraction separated in theseparation step;

(f) a naphthalene collecting step of separating and collectingnaphthalene compounds including at least naphthalene, from a heavy oilfraction having 9 or more carbon numbers that is obtainable from theliquid fraction separated in the separation step;

(g) a hydrogen supply step of supplying the hydrogen collected in thehydrogen collecting step to a hydrogenation reaction step;

(h) a hydrogenation reaction step of hydrogenating the fractionremaining after naphthalene compounds have been separated in thenaphthalene collecting step; and

(i) a recycling step of recycling the hydrogenation reaction productobtained in the hydrogenation reaction step to the cracking reformingreaction step.

It should be noted, among the steps of (a) to (i), the steps of (a),(b), (e) and (f) are essential steps for the invention related to claim1 of the invention, and the other steps are optional steps.

Hereinafter, the various steps will be specifically described.

<Cracking Reforming Reaction Step>

In the cracking reforming reaction step, a feedstock is brought intocontact with a catalyst for monocyclic aromatic hydrocarbon production,polycyclic aromatic hydrocarbons are partially hydrogenated by ahydrogen transfer reaction from saturated hydrocarbons by using thesaturated hydrocarbons included in the feedstock as a hydrogen donatingsource, and the polycyclic aromatic hydrocarbons are converted tomonocyclic aromatic hydrocarbons by ring-opening. Furthermore,conversion to monocyclic aromatic hydrocarbons can also be achieved bycyclizing and dehydrogenating saturated hydrocarbons obtainable from thefeedstock or in a cracking step. Also, monocyclic aromatic hydrocarbonshaving 6 to 8 carbon numbers can also be obtained by cracking monocyclicaromatic hydrocarbons having 9 or more carbon numbers. Thereby, aproduct including monocyclic aromatic hydrocarbons having 6 to 8 carbonnumbers and a heavy oil fraction having 9 or more carbon numbers isobtained. This product includes, in addition to the monocyclic aromatichydrocarbons and the heavy oil fraction, hydrogen, methane, ethane,ethylene, LPG (propane, propylene, butane, butene and the like), and thelike. Furthermore, the heavy oil fraction includes large amounts ofnaphthalene, methylnaphthalene, and dimethylnaphthalene. Meanwhile, inthe present specification, these naphthalene, methylnaphthalene anddimethylnaphthalene are collectively described as “naphthalenecompounds”.

In the cracking reforming reaction step, components such asnaphthenobenzenes, paraffins and naphthenes in the feedstock can beeliminated by producing monocyclic aromatic hydrocarbons, and polycyclicaromatic hydrocarbons can be converted mainly to naphthalene compoundswith a high added value, such as naphthalene, methylnaphthalene anddimethylnaphthalene, which have fewer side chains, by cleaving alkylside chains simultaneously with the conversion of polycyclic aromatichydrocarbons to monocyclic aromatic hydrocarbons. That is, in thepresent cracking reforming reaction step, monocyclic aromatichydrocarbons can be produced with high yield, and at the same time,other components having a boiling point close to that of naphthalenecompounds can be reduced as much as possible. Therefore, when the amountof production of naphthalene compounds having short side chains isincreased, and the content ratio of naphthalene compounds in the oilproduced by the cracking reforming reaction is increased, collection ofnaphthalene compounds that will be described below can be efficientlycarried out.

Light cycle oil or the like that is used as a main feedstock originallycontains a large proportion of naphthalene compounds, but at the sametime, contains large proportions of other components such asnaphthenobenzenes and paraffins. Therefore, the content ratio ofnaphthalene compounds relative to the total amount of the feedstock issmall, and it is very difficult to directly separate and purifynaphthalene compounds from the feedstock. In the case of performingseparation and purification of naphthalene compounds from the feedstock,high energy consumption type processes such as crystallization should beemployed, which is not preferable.

The present cracking reforming reaction step enables the proportion ofuseful aromatic hydrocarbons that can be collected, to be increased to alarge extent as described above.

(Feedstock)

The feedstock that is used in the present embodiment is an oil having a10 vol % distillation temperature of 140° C. or higher and a 90 vol %distillation temperature of 380° C. or lower. Since oil having a 10 vol% distillation temperature of lower than 140° C. is light, monocyclicaromatic hydrocarbons are produced by very light fraction, and the oilis not suitable for the present embodiment. Furthermore, when an oilhaving a 90 vol % distillation temperature of higher than 380° C. isused, not only the yield of monocyclic aromatic hydrocarbons is lowered,but also the amount of coke deposition on the catalyst for monocyclicaromatic hydrocarbon production increases, and the catalytic activitytends to undergo a rapid decrease.

The 10 vol % distillation temperature of the feedstock is preferably150° C. or higher, and the 90 vol % distillation temperature of thefeedstock is preferably 360° C. or lower. On the other hand, the upperlimit of the 10 vol % distillation temperature and the lower limit ofthe 90 vol % distillation temperature of the feedstock are notparticularly limited, but from the viewpoint that monocyclic aromatichydrocarbons having 6 to 8 carbon numbers and naphthalene compounds canbe efficiently produced, the 10 vol % distillation temperature ispreferably 210° C. or lower, and the 90 vol % distillation temperatureis preferably 240° C. or higher.

Meanwhile, the 10 vol % distillation temperature and 90 vol %distillation temperature as used herein mean values measured accordingto JES K2254 “Petroleum products—Distillation test methods”.

Examples of the feedstock having a 10 vol % distillation temperature of140° C. or higher and a 90 vol % distillation temperature of 380° C. orlower include LCO produced by a FCC units, a hydrogenated purified oilof LCO, other cracked light oils such as hydrogenated cracked light oiland thermally cracked light oil, coal liquefied oil, heavy oilhydrogenated cracked purified oil, straight run kerosene, straight runlight oil, coker kerosene, coker light oil, and purified oil obtained byhydrogenation cracking oil sand.

Furthermore, if the feedstock contains a large amount of polycyclicaromatic hydrocarbons, the yield of monocyclic aromatic hydrocarbonsdecreases. Therefore, the content of polycyclic aromatic hydrocarbons(polycyclic aromatic content) in the feedstock is preferably 50 vol % orless, and more preferably 40 vol % or less. However, as will bedescribed below, when it is intended to further increase the yield ofnaphthalene (or naphthalene compounds) produced together with themonocyclic aromatic hydrocarbons, the polycyclic aromatic content in thefeedstock may be adjusted to, for example, 50 vol % or more. However,even in that case, the content of aromatic hydrocarbons having 3 or morerings is preferably set to 30 vol % or less, and more preferably set to15 vol % or less.

The term polycyclic aromatic content as used herein means the totalvalue of the content of bicyclic aromatic hydrocarbons (bicyclicaromatic content) and the content of aromatic hydrocarbons with 3 ormore rings (tricyclic or higher-cyclic aromatic content), which aremeasured according to JPI-5S-49 “Petroleum products—Hydrocarbon typetest methods—high performance liquid chromatographic method”, oranalyzed by an FID gas chromatographic method. Hereinbelow, when thecontents of polycyclic aromatic hydrocarbons, bicyclic aromatichydrocarbons, and tricyclic or higher-cyclic aromatic hydrocarbons areexpressed in vol %, the content was measured by the method of JPI-5S-49,while when the content is expressed in mass %, the content was measuredby an FID gas chromatographic method.

(Reaction Mode)

Examples of the reaction mode employed when the feedstock is broughtinto contact with a catalyst for monocyclic aromatic hydrocarbons toreact therewith, include a fixed bed, a mobile bed, and a fluidized bed.According to the present embodiment, since heavy oil components are usedas a feedstock, a fluidized bed which is capable of continuouslyremoving the coke component adhering to the catalyst and is capable ofstably carrying out the reaction is preferred. Particularly, acontinuously regenerative type fluidized bed in which a catalyst iscirculated between a reactor and a regenerator so thatreaction-regeneration can be continuously repeated, is particularlypreferred. When brought into contact with the catalyst for monocyclicaromatic hydrocarbon production, the feedstock is preferably in a gasphase. Furthermore, the feedstock may also be diluted with a gas asnecessary.

(Catalyst for Monocyclic Aromatic Hydrocarbon Production)

The catalyst for monocyclic aromatic hydrocarbon production contains acrystalline aluminosilicate.

[Crystalline Aluminosilicate]

From the viewpoint of further increasing the yield of monocyclicaromatic hydrocarbons, the crystalline aluminosilicate is preferably azeolite with medium-sized pores and/or a zeolite with large-sized pores.

The zeolite with medium-sized pores is a zeolite having a 10-memberedring skeletal structure, and examples of the zeolite with medium-sizedpores include zeolites having AEL type, EUO type, FER type, HEU type,MEL type, MFI type, NES type, TON type, and WEI type crystal structures.Among these, MFI type zeolite is preferred from the viewpoint that theyield of monocyclic aromatic hydrocarbons can be further increased.

The zeolite with large-sized pores is a zeolite having a 12-memberedring skeletal structure, and examples of the zeolite with large-sizedpores include zeolites having AFI type, ATO type, BEA type, CON type,FAU type, GME type, LTL type, MOR type, MTW type, and OFF type crystalstructures. Among these, from the viewpoint that the total yield ofmonocyclic aromatic hydrocarbons and aliphatic hydrocarbons having 3 to4 carbon numbers can be further increased, BEA type zeolite ispreferred.

However, as will be described below, when it is intended to furtherincrease the yield of naphthalene (or naphthalene compounds) that areproduced together with monocyclic aromatic hydrocarbons, a catalystcontaining a crystalline aluminosilicate other than the MFI type or BEAtype zeolite described above may also be used.

Furthermore, the crystalline aluminosilicate may also contain a zeolitewith small-sized pores, having a 10-membered or fewer-membered ringskeletal structure, and a zeolite with ultra-large-sized pores, having a14-membered or more-membered ring skeletal structure, in addition to thezeolite with medium-sized pores and the zeolite with large-sized pores.

Here, examples of the zeolite with small-sized pores include zeoliteshaving ANA type, CHA type, ERI type, GIS type, KFI type, LTA type, NATtype, PAU type and YUG type crystal structures.

Examples of the zeolite with ultra-large-sized pores include zeoliteshaving CLO type and VPI type crystal structures.

When the cracking reforming reaction step is carried out as a fixed bedreaction, the content of the crystalline aluminosilicate in the catalystfor monocyclic aromatic hydrocarbon production is preferably 60 mass %to 100 mass %, more preferably 70 mass % to 100 mass %, and particularlypreferably 90 mass % to 100 mass %, when the total amount of thecatalyst for monocyclic aromatic hydrocarbon production is designated as100 mass %. When the content of the crystalline aluminosilicate is 60mass % or more, the yield of monocyclic aromatic hydrocarbons can besufficiently increased. Furthermore, the yield of naphthalene compoundscan also be raised to a relatively high level.

When the cracking reforming reaction step is carried out by a fluidizedbed reaction, the content of the crystalline aluminosilicate in thecatalyst for monocyclic aromatic hydrocarbon production is preferably 20mass % to 60 mass %, more preferably 30 mass % to 60 mass %, andparticularly preferably 35 mass % to 60 mass %, when the total amount ofthe catalyst for monocyclic aromatic hydrocarbon production isdesignated as 100 mass %. When the content of the crystallinealuminosilicate is 20 mass % or more, the yield of monocyclic aromatichydrocarbons can be sufficiently increased. Furthermore, the yield ofnaphthalene compounds can also be raised to a relatively high level.Meanwhile, when the content of the crystalline aluminosilicate is morethan 60 mass %, the content of a binder that can be incorporated intothe catalyst is decreased, and the catalyst may not be suitable forfluidized bed applications.

[Phosphorus and Boron]

The catalyst for monocyclic aromatic hydrocarbon production preferablycontains phosphorus and/or boron. When the catalyst for monocyclicaromatic hydrocarbon production contains phosphorus and/or boron, adecrease in the yield of monocyclic aromatic hydrocarbons over time canbe prevented, and coke production on the catalyst surface can besuppressed.

Examples of the method for incorporating phosphorus to the catalyst formonocyclic aromatic hydrocarbon production include a method ofsupporting phosphorus on a crystalline aluminosilicate, a crystallinealuminogallosilicate or a crystalline aluminozincosilicate, by an ionexchange method, an impregnation method or the like; a method ofincorporating a phosphorus compound at the time of zeolite synthesis andsubstituting a portion in the skeleton of a crystalline aluminosilicatewith phosphorus; and a method of using a crystallization acceleratorcontaining phosphorus at the time of zeolite synthesis. The phosphateion-containing aqueous solution used at that time is not particularlylimited, but solutions prepared by dissolving phosphoric acid,diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and otherwater-soluble phosphates in water at arbitrary concentrations can bepreferably used.

Examples of the method of incorporating boron into the catalyst formonocyclic aromatic hydrocarbon production include a method ofsupporting boron on a crystalline aluminosilicate, a crystallinealuminogallosilicate or a crystalline aluminozincosilicate, by an ionexchange method, an impregnation method or the like; a method ofincorporating a boron compound at the time of zeolite synthesis andsubstituting a portion of the skeleton of a crystalline aluminosilicatewith boron; and a method of using a crystallization acceleratorcontaining boron at the time of zeolite synthesis.

The content of phosphorus and/or boron in the catalyst for monocyclicaromatic hydrocarbon production is preferably 0.1 mass % to 10 mass %,relative to the total weight of the catalyst, and the lower limit ismore preferably 0.5 mass % or more, while the upper limit is morepreferably 9 mass % or less, and particularly preferably 8 mass % orless. When the content of phosphorus and/or boron relative to the totalweight of the catalyst is 0.1 mass % or more, a decrease in the yield ofmonocyclic aromatic hydrocarbons over time can be prevented, and whenthe content is 10 mass % or less, the yield of monocyclic aromatichydrocarbons can be increased.

[Gallium and Zinc]

In the catalyst for monocyclic aromatic hydrocarbon production, galliumand/or zinc can be incorporated as necessary. When gallium and/or zincis incorporated, the production proportion of monocyclic aromatichydrocarbons can be further increased.

The form of gallium incorporation in the catalyst for monocyclicaromatic hydrocarbon production may be a form in which gallium isincorporated into the lattice skeleton of a crystalline aluminosilicate(crystalline aluminogallosilicate), a form in which gallium is supportedon a crystalline aluminosilicate (gallium-supporting crystallinealuminosilicate), or both of them.

The form of zinc incorporation in the catalyst for monocyclic aromatichydrocarbon production may be a form in which zinc is incorporated intothe lattice skeleton of a crystalline aluminosilicate (crystallinealuminozincosilicate), a form in which zinc is supported on acrystalline aluminosilicate (zinc-supporting crystallinealuminosilicate), or both of them.

The crystalline aluminogallosilicate and crystallinealuminozincosilicate have a structure in which SiO₄, AlO₄ and GaO₄/ZnO₄structures exist in the skeletal structure. Furthermore, the crystallinealuminogallosilicate and crystalline aluminozincosilicate are obtainedby, for example, gel crystallization based on hydrothermal synthesis, amethod of inserting gallium or zinc into the lattice skeleton of acrystalline aluminosilicate, or a method of inserting aluminum into thelattice skeleton of a crystalline gallosilicate or a crystallinezincosilicate.

The gallium-supporting crystalline aluminosilicate is a material inwhich gallium is supported on a crystalline aluminosilicate according toa known method such as an ion exchange method or an impregnation method.The gallium source that is used at that time is not particularlylimited, but examples thereof include gallium salts such as galliumnitrate and gallium chloride, and gallium oxide.

The zinc-supporting crystalline aluminosilicate is a compound in whichzinc is supported on a crystalline aluminosilicate according to a knownmethod such as an ion exchange method or an impregnation method. Thezinc source that is used at that time is not particularly limited, butexamples thereof include zinc salts such as zinc nitrate and zincchloride, and zinc oxide.

When the catalyst for monocyclic aromatic hydrocarbon productioncontains gallium and/or zinc, the content of gallium and/or zinc in thecatalyst for monocyclic aromatic hydrocarbon production is preferably0.01 mass % to 5.0 mass %, and more preferably 0.05 mass % to 1.5 mass%, relative to 100 mass % of the total amount of the catalyst. When thecontent of gallium and/or zinc is 0.01 mass % or greater, the productionproportion of monocyclic aromatic hydrocarbons can be further increased.When the content is 5.0 mass % or less, the yield of monocyclic aromatichydrocarbons can be further increased.

[Shape]

The catalyst for monocyclic aromatic hydrocarbon production is producedinto, for example, a powder form, a particulate form, a pellet form orthe like according to the reaction mode. For example, in the case of afluidized bed, the catalyst is produced in a powder form, and in thecase of a fixed bed, the catalyst is produced in a particulate form or apellet form. The average particle size of the catalyst used in afluidized bed is preferably 30 μm to 180 μm, and more preferably 50 μmto 100 μm. Furthermore, the apparent density of the catalyst used in afluidized bed is preferably 0.4 g/cc to 1.8 glee, and more preferably0.5 g/cc to 1.0 g/cc.

Meanwhile, the average particle size represents the particle size for aproportion of 50 mass % in a particle size distribution obtained byclassification using sieves, and the apparent density is a valuemeasured by the method of JIS Standards R9301-2-3.

In the case of obtaining a particulate or pellet-like catalyst, an oxidewhich is inert to the catalyst is incorporated as a binder as necessary,and the mixture may be molded by using various molding machines.

When the catalyst for monocyclic aromatic hydrocarbon productioncontains an inorganic oxide such as a binder, a binder containingphosphorus may also be used.

(Reaction Temperature)

The reaction temperature at the time of bringing the feedstock intocontact with the catalyst for monocyclic aromatic hydrocarbon productionto react therewith is not particularly limited, but the reactiontemperature is preferably 400° C. to 650° C., and more preferably 450°C. to 650° C. When the reaction temperature is 400° C. or higher, thereaction of the feedstock can be facilitated. When the reactiontemperature is from 450° C. to 650° C., the yield of monocyclic aromatichydrocarbons can be sufficiently increased, and the yield of naphthalenecompounds can also be raised to a relatively high level.

(Reaction Pressure)

The reaction pressure employed when the feedstock is brought intocontact with the catalyst for monocyclic aromatic hydrocarbon productionto react therewith is preferably set to 1.5 MPaG or less, and morepreferably to 1.0 MPaG or less. When the reaction pressure is 1.5 MPaGor less, by-production of light gas can be suppressed, and also,pressure resistance of the reaction apparatus can be lowered.Furthermore, when the reaction pressure is from 0.1 MPaG to 1.5 MPaG,the yield of monocyclic aromatic hydrocarbons can be sufficientlyincreased, and the yield of naphthalene compounds can also be raised toa relatively high level.

(Contact Time)

The contact time between the feedstock and the catalyst for monocyclicaromatic hydrocarbon production is not particularly limited so long asthe desired reaction substantially proceeds. However, for example, thetime for gas passage on the catalyst for monocyclic aromatic hydrocarbonproduction is preferably 1 second to 300 seconds, and the lower limit ismore preferably 5 seconds or longer, while the upper limit is morepreferably 150 seconds or shorter. When the contact time is 1 second orlonger, the reaction can be achieved reliably, and when the contact timeis 300 seconds or shorter, accumulation of carbon substances on thecatalyst caused by coking or the like can be suppressed. Also, theamount of light gas generated by cracking can be suppressed.Furthermore, the yield of monocyclic aromatic hydrocarbons can besufficiently increased, and the yield of naphthalene compounds can alsobe raised to a relatively high level.

<Separation Step>

In the separation step, the product produced in the cracking reformingreaction step is separated into multiple fractions.

In order to separate the product into plural fractions, knowndistillation apparatuses and gas-liquid separation apparatuses may beused. Examples of the distillation apparatuses include apparatuses thatare capable of separating by distillation of multiple fractions by amultistage distillation apparatus such as a stripper. Examples of thegas-liquid separation apparatuses include apparatuses each equipped witha gas-liquid separating tank, a product inlet pipe for introducing theproduct into the gas-liquid separating tank, a gas component dischargepipe provided in the upper part of the gas-liquid separating tank, and aliquid component discharge pipe provided in the lower part of the gasliquid separating tank.

In the separation step, it is preferable to separate at least gascomponents and a liquid fraction, and the liquid fraction may be furtherseparated into plural fractions. An example of the separation step maybe a form of process by which the reaction product is separated into gascomponents mainly including components having 4 or fewer carbon numbers(for example, hydrogen, methane, ethane, and LPG) and a liquid fraction.Furthermore, another example of the separation step may be a form ofprocess by which the reaction product is separated into gas componentsincluding components having 2 or fewer carbon numbers (for example,hydrogen, methane and ethane) and a liquid fraction. Furthermore,another example of the separation step may be a form of process by whichthe liquid fraction is separated into LPG, a fraction containingmonocyclic aromatic hydrocarbons, and a heavy oil fraction. Furthermore,another example of the separation step may be a form of process by whichthe liquid fraction is separated into LPG (for example, propylene,propane, butene, and butane), a fraction containing monocyclic aromatichydrocarbons, and plural heavy oil fractions. Furthermore, when afluidized bed is employed as the reaction mode for the crackingreforming reaction step, the catalyst powder and the like to beincorporated may be removed in the present step. However, for the heavyoil fraction, naphthalene compounds may be separated singly, or theheavy oil fraction may also be collectively fractionated withoutseparating into plural fractions. The boiling point range of thefraction containing monocyclic aromatic hydrocarbons having 6 to 8carbon numbers is preferably 78° C. to 150° C., and the boiling pointrange of the heavy oil fraction primarily containing naphthalenecompounds is preferably 210° C. to 270° C.

<Purification and Collection Step>

The purification and collection step purifies and collects themonocyclic aromatic hydrocarbons having 6 to 8 carbon numbers obtainedin the separation step.

In this purification and collection step, the liquid fraction issufficiently fractionated in the separation step, and when monocyclicaromatic hydrocarbons having 6 to 8 carbon numbers are separated intobenzene/toluene/xylene, a step of purifying and collecting therespective components is employed. Furthermore, when the monocyclicaromatic hydrocarbons having 6 to 8 carbon numbers are collectivelyfractionated, a step of collecting these monocyclic aromatichydrocarbons, subsequently separating the hydrocarbons intobenzene/toluene/xylene, and then purifying and collecting the respectivecomponents is employed.

In the case where the liquid fraction is not satisfactorily fractionatedin the separation step, and when the monocyclic aromatic hydrocarbonshaving 6 to 8 carbon numbers are collected, the liquid fraction containsa large proportion of a fraction other than the monocyclic aromatichydrocarbons, these fractions may be separated and supplied to, forexample, the hydrogenation reaction step or naphthalene collection stepthat will be described below. Particularly, among the fractions otherthan monocyclic aromatic hydrocarbons, a fraction heavier than themonocyclic aromatic hydrocarbons (a heavy oil fraction having 9 or morecarbon numbers) is preferably supplied to the naphthalene collectionstep. This is because the heavy oil fraction having 9 or more carbonnumbers contains polycyclic aromatic hydrocarbons as a main component,and contains a large proportion of naphthalene or alkylnaphthalenes inparticular.

Naphthalene Collecting Step>

In the naphthalene collecting step, naphthalene compounds including atleast naphthalene are separated and collected from a heavy oil fractionhaving 9 or more carbon numbers obtainable from the liquid fractionseparated in the separation step.

In this naphthalene collecting step, in the case where the heavy oilfraction separated in the separation step is separated into a heavy oilfraction primarily containing naphthalene compounds in particular and aheavy oil fraction other than that, the heavy oil fraction containingnaphthalene compounds is purified, and thus naphthalene compounds areseparated and collected. Furthermore, in the separation step, when theheavy oil fraction having 9 or more carbon numbers is collectivelyfractionated without dividing the heavy oil fraction having 9 or morecarbon numbers into plural fractions, the heavy oil fraction isseparated into a fraction containing naphthalene compounds, specificallynaphthalene compounds including naphthalene, methylnaphthalene anddimethylnapthalene, and a fraction other than that, and the naphthalenecompounds including at least naphthalene are purified and collected.

Meanwhile, in order to separate the heavy oil fraction into multiplefractions, a known distillation apparatus (distillation column) such asthat used in the separation step may be used.

Since the components having a boiling point close to that of thenaphthalene compounds in the oil produced by a cracking reformingreaction have been reduced to a large extent by going through thecracking reforming reaction step, in the present naphthalene collectingstep, naphthalene can be separated with high purity, purified andcollected by using only a known distillation apparatus such as that usedin the separation step. For example, naphthalene can be purified to apurity of about 80% to 98% and then can be collected. Meanwhile, thepurity of naphthalene thus collected is determined on the basis ofreduction of the number and the production amount of components having aboiling point close to that of naphthalene that remains in the crackingreforming reaction step, and the performance of the distillationapparatus. When naphthalene is collected with a purity of 95% or higher,the naphthalene can be dealt with as a product which is generallydistributed as crude naphthalene and has a commercial value, and inregard to naphthalene with a purity of less than 95%, for example, about80% to 95%, this can be made into crude naphthalene as a chemicalproduct by performing a purification treatment later and increasing thepurity to 95% or higher. Furthermore, a fraction having a purity of 95%or higher can also be subjected to a further purification treatment andcan be converted to naphthalene with higher purity. Examples of thepurification treatment methods in this case include crystallization.

In the naphthalene collecting step, so long as naphthalene can beseparated and collected, naphthalene compounds other than naphthalenemay be collectively separated, purified and collected asalkylnaphthalenes, or may be individually separated, purified andcollected as methylnaphthalene, dimethylnaphthalene and the like. Inthis case, methylnaphthalene and dimethylnaphthalene are respectivelypurified to a purity of about 80% to 95% and collected. Thereafter, thecomponents are respectively purified to a purity demanded as chemicalproducts.

Here, in this naphthalene collecting step, a fraction other than thedesired naphthalene, methylnaphthalene and dimethylnaphthalene is alsoobtained. This fraction is sent out of the system, and for example,after treatments such as purification are carried out as necessary, thefraction is used as a base material for light oil/kerosene.Alternatively, the fraction is sent to the hydrogenation reaction stepthat will be described below, and after this step, the fraction isrecycled.

Meanwhile, in the present embodiment shown in FIG. 1, the naphthalenecollecting step is composed of a single step. In the naphthalenecollecting step, first, the step may be divided into multiple steps byproviding a step of separating and collecting naphthalene from a heavyoil fraction having 9 or more carbon numbers, and then providing stepsof respectively fractionating and collecting methylnaphthalene,dimethylnaphthalene and the like, and naphthalene, methylnaphthalene anddimethylnaphthalene may be respectively fractionated and collected.Furthermore, a fraction other than these is used as a base material forlight oil/kerosene, or is subjected to a hydrogenation reaction step orthe like and then supplied to the feedstock for recycling.

<Hydrogenation Reaction Step>

In this hydrogenation reaction step, a portion or the entirety of theremaining fraction obtained after naphthalene has been separated in thenaphthalene collecting step is supplied to this hydrogenation reactionstep, and this fraction is hydrogenated. Here, if only naphthalene isseparated and collected in the naphthalene collecting step, andalkylnaphthalenes such as methylnaphthalene and dimethylnaphthalene arenot separated and collected, these alkylnaphthalenes constitute the“remaining fraction obtained after naphthalene has been separated” asdescribed above, and are supplied to the hydrogenation reaction step.Meanwhile, the remaining fraction obtained after naphthalene compoundshave been separated, which was not supplied to the hydrogenationreaction step, may also be used as a fuel base material for lightoil/kerosene and the like.

Specifically, the remaining fraction obtained by naphthalene compoundshave been separated in the naphthalene collecting step, and hydrogen aresupplied to a hydrogenation reactor, and at least a portion of thepolycyclic aromatic hydrocarbons included in the remaining fractionobtained after naphthalene compounds have been separated is subjected tohydrogenation by using a hydrogenation catalyst.

The polycyclic aromatic hydrocarbons are not particularly limited, butit is preferable to hydrogenate the polycyclic aromatic hydrocarbonsuntil the number of aromatic rings becomes 1 or less on the average.When the polycyclic aromatic hydrocarbons are hydrogenated until thenumber of aromatic rings becomes 1 or less on the average, when thepolycyclic aromatic hydrocarbons are recycled to the cracking reformingreaction step, the hydrogenation reaction product can be easilyconverted to monocyclic aromatic hydrocarbons.

Furthermore, in order to further increase particularly the yield ofmonocyclic aromatic hydrocarbons, the content of polycyclic aromatichydrocarbons in the hydrogenation reaction product obtainable in thehydrogenation reaction step is preferably adjusted to 20 mass % or less,and more preferably 10 mass % or less. The content of polycyclicaromatic hydrocarbons in the hydrogenation reaction product ispreferably smaller than the content of polycyclic aromatic hydrocarbonsin the feedstock, and the content can be reduced as the amount of thehydrogenation catalyst is increased, and as the reaction pressure isincreased.

However, it is not necessary to carry out the hydrogenation treatmentuntil the entirety of the polycyclic aromatic hydrocarbons becomessaturated hydrocarbons. Excessive hydrogenation tends to cause anincrease in the amount of hydrogen consumption and an increase in theamount of heat generation.

Furthermore, when it is intended to prioritize an enhancement of theyield of naphthalene (naphthalene compounds) to an enhancement of theyield of monocyclic aromatic hydrocarbons, the content of polycyclicaromatic hydrocarbons in the hydrogenation reaction product obtainablein the hydrogenation reaction step is preferably adjusted to 20 mass %or more.

In the present embodiment, hydrogen produced as a by-product in thecracking reforming reaction step can also be utilized. That is, hydrogenis collected in the hydrogenation collecting step that will be describedbelow from the gas components obtained in the separation step, and inthe hydrogen supply step, the collected hydrogen is supplied to thehydrogenation reaction step.

Regarding the reaction mode for the hydrogenation reaction step, a fixedbed is suitably employed.

As the hydrogenation catalyst, known hydrogenation catalysts (forexample, a nickel catalyst, a palladium catalyst, anickel-molybdenum-based catalyst, a cobalt-molybdenum-based catalyst, anickel-cobalt-molybdenum-based catalyst, and a nickel-tungsten-basedcatalyst) can be used.

The reaction temperature may vary depending on the hydrogenationcatalyst used, but the reaction temperature is usually set to the rangeof 100° C. to 450° C., more preferably 200° C. to 400° C., and even morepreferably 250° C. to 380° C.

The reaction pressure may vary depending on the hydrogenation catalystor feedstock used, but the reaction pressure is preferably set to therange of 0.7 MPa to 13 MPa, more preferably set to 1 MPa to 10 MPa, andparticularly preferably set to 1 MPa to 7 MPa. When the reactionpressure is adjusted to 13 MPa or less, a hydrogenation reactor having alow durability pressure can be used, and the cost of equipment can bereduced.

On the other hand, the reaction pressure is preferably 0.7 MPa orgreater in view of the yield of the hydrogenation reaction.

The amount of hydrogen consumption is preferably 3000 scfb (506 Nm³/m³)or less, more preferably 2500 scfb (422 Nm³/m³) or less, and even morepreferably 1500 scfb (253 Nm³/m³) or less.

On the other hand, the amount of hydrogen consumption is preferably 300scfb (50 Nm³/m³) or greater in view of the yield of the hydrogenationreaction.

The liquid hourly space velocity (LHSV) is preferably set to from 0.1h⁻¹ to 20 h⁻¹, and more preferably set to from 0.2 h⁻¹ to 10 h⁻¹. Whenthe LHSV is set to 20 h⁻¹ or less, polycyclic aromatic hydrocarbons canbe sufficiently hydrogenated at a lower hydrogenation reaction pressure.On the other hand, when the LHSV is set to 0.1 h⁻¹ or higher, anexcessive increase in the size of hydrogenation reactors can be avoided.

<Hydrogen Collecting Step>

In the hydrogen collecting step, hydrogen is collected from the gascomponents obtained in the separation step.

Regarding the method for collecting hydrogen, there are no particularlimitations so long as hydrogen and other gases that are included in thegas components obtained in the separation step can be separated, andexamples thereof include a pressure swing adsorption method (PSAmethod), a low temperature separation processing method, and a membraneseparation method.

Conventionally, the amount of hydrogen collected in the hydrogencollecting step is larger than the amount required for hydrogenating theheavy oil fraction or the light oil/kerosene fraction described above.

<Hydrogen Supply Step>

In the hydrogen supply step, hydrogen obtained in the hydrogencollecting step is supplied to the hydrogenation reactor of thehydrogenation reaction step. The amount of hydrogen supplied at thattime is adjusted according to the amount of the remaining fractionobtained after naphthalene compounds have been separated in thenaphthalene collecting step, which is supplied to the hydrogenationreaction step. Furthermore, if necessary, the hydrogen pressure isregulated.

By including such a hydrogen supply step as that of the presentembodiment, the remaining fraction obtained after naphthalene compoundshave been separated in the naphthalene collecting step described abovecan be hydrogenated by using the hydrogen produced as a by-product inthe cracking reforming reaction step, and efficient operation of theapparatus can be promoted.

<Recycling Step>

In the recycling step, the hydrogenation reaction product is mixed withthe feedstock, and the mixture is recycled to the cracking reformingreaction step. The hydrogenation reaction product is a product obtainedby allowing the remaining fraction obtained after naphthalene compoundshave been separated in the naphthalene collecting step, to react in thehydrogenation reaction step.

When such a hydrogenation reaction product is recycled to the crackingreforming reaction step, monocyclic aromatic hydrocarbons or naphthalenecompounds can be obtained by using the heavy oil fraction (excludingnaphthalene compounds), which is a by-product, as a feedstock.Therefore, not only the amount of by-product can be reduced, but also,the amount of monocyclic aromatic hydrocarbons or naphthalene compoundsproduced can be increased. Furthermore, since saturated hydrocarbons arealso produced by hydrogenation, the hydrogen transfer reaction can beaccelerated in the cracking reforming reaction step. From these matters,the general yield of monocyclic aromatic hydrocarbons relative to theamount of the feedstock supplied can be increased, and also, the yieldof naphthalene compounds can also be increased.

Meanwhile, when the remaining fraction obtained by separatingnaphthalene compounds in the naphthalene collecting step is recycleddirectly to the cracking reforming reaction step without performing ahydrogenation treatment, since the reactivity of polycyclic aromatichydrocarbons is low, an increase in the yield of monocyclic aromatichydrocarbons can be hardly expected. However, an increase in the yieldof naphthalene compounds can be promoted.

<LPG Collecting Step>

In the LPG collecting step, LPG that is produced as a by-product in thecracking reforming reaction step is collected from the liquid fractionseparated in the separation step.

In this LPG collecting step, a liquid fraction having 3 or 4 carbonnumbers, that is, propylene, propane, butene and butane are purified andcollected as LPG. In the oil produced by the cracking reforming reactionin the method for producing aromatic hydrocarbons of the presentembodiment, unlike the products of hydrogenation cracking and the likein conventional petroleum purification processes, more of olefins suchas propylene and butene are present. Therefore, if necessary, collectionof olefins by hydrogenation or rectification can also be achieved.

As explained above, in the method for producing aromatic hydrocarbons ofthe present embodiment, monocyclic aromatic hydrocarbons having 6 to 8carbon numbers can be produced with a relatively high yield from afeedstock containing polycyclic aromatic hydrocarbons, and as otherchemical products, naphthalene compounds including naphthalene, orolefin compounds such as propylene, propane, butene and butane can alsobe produced.

Particularly, in regard to naphthalene, it has been conventional ingeneral to produce naphthalene according to a crystallization method bywhich coal tar distillate oil is cooled, and thereby crystals areprecipitated. However, the crystallization method requires complicatedsteps, and there is a problem that the production cost is high.

In contrast to this, the method for producing aromatic hydrocarbons ofthe present embodiment can obtain naphthalene with a relatively highpurity, only by adding a naphthalene collecting step, or if necessary, anaphthalene compound separation and collection step to the process forproducing monocyclic aromatic hydrocarbons having 6 to 8 carbon numbers.Therefore, in regard to the production cost for naphthalene (ornaphthalene compounds), when the portion for producing monocyclicaromatic hydrocarbons having 6 to 8 carbon numbers is deducted, theproduction cost is markedly decreased as compared with conventionalmethods according to a crystallization method. Therefore, naphthalene(or naphthalene compounds) can be provided at low cost.

Other Embodiments

The invention is not intended to be limited to the embodiment examplesdescribed above, and various modifications can be made to the extentthat the gist of the invention is maintained.

For example, in regard to the method shown in FIG. 1, a hydrogenationreaction step of hydrogenating a portion of the liquid componentsseparated in the separation process may be provided between theseparation process and the purification and collection process. In thepurification and collection step, the hydrogenation reaction productobtained in the hydrogenation reaction step may be distilled, andmonocyclic aromatic hydrocarbons may be purified and collected.

Furthermore, a portion of the heavy oil fraction separated in theseparation step may also be supplied to the hydrogenation reaction stepwithout going through the naphthalene collecting step, and the portionmay also be hydrogenated and recycled to the cracking reforming reactionprocess.

Furthermore, in these methods or in the method shown in FIG. 1,regarding hydrogen used in the hydrogenation reaction step, hydrogenobtained in a known hydrogen production method may be used instead ofthe hydrogen produced as a by-product in the cracking reforming reactionstep, or hydrogen produced as a by-product in another contact crackingmethod may also be used.

EXAMPLES

Hereinafter, the invention will be more specifically described based onExamples and Comparative Examples, but the invention is not intended tobe limited by these Examples.

[Preparation Example for Catalyst for Monocyclic Aromatic HydrocarbonProduction]

Preparation of Catalyst Containing Ga and Phosphorus-SupportedCrystalline Aluminosilicate:

A solution (A) containing sodium silicate (J sodium silicate No. 3,SiO₂: 28 mass % to 30 mass %, Na: 9 mass % to 10 mass %, balance water,manufactured by Nippon Chemical Industrial Co., Ltd.): 1706.1 g andwater: 2227.5 g, and a solution (B) containing Al₂(SO₄)₃.14-18H₂O(reagent grade, manufactured by Wako Pure Chemical Industries, Ltd.):64.2 g, tetrapropylammonium bromide: 369.2 g, H₂SO₄ (97 mass %): 152.1g, NaCl: 326.6 g and water: 2975.7 g were each prepared.

Subsequently, while the solution (A) was stirred at room temperature,the solution (B) was slowly added to the solution (A).

The mixture thus obtained was vigorously stirred for 15 minutes in amixer, and the gel was crushed to obtain a milky homogenously finestate.

Subsequently, this mixture was placed in an autoclave made of stainlesssteel, and a crystallization operation was carried out underself-pressure under the conditions of a temperature of 165° C., a timeof 72 hours, and a stirring speed of 100 rpm. After completion of thecrystallization operation, the product was filtered to collect a solidproduct, and washing and filtration was repeated 5 times by using about5 liters of deionized water. The solid obtained by filtration was driedat 120° C., and the solid was calcined at 550° C. for 3 hours under astream of air.

It was confirmed by an X-ray diffraction analysis (model name: Rigaku.RINT-2500V) that the calcination product thus obtained had an MFIstructure. Furthermore, the SiO₂/Al₂O₃ ratio (molar ratio) obtained by afluorescence X-ray analysis (model name: Rigaku ZSX101e) was 64.8.Furthermore, the content of the aluminum element contained in thelattice structure calculated from these results was 1.32 mass %.

Subsequently, a 30 mass % aqueous solution of ammonium nitrate was addedat a ratio of 5 mL per 1 g of the calcination product thus obtained, andthe mixture was heated and stirred at 100° C. for 2 hours, subsequentlyfiltered and washed with water. This operation was repeated 4 times, andthen the mixture was dried at 120° C. for 3 hours. Thus, an ammoniumtype crystalline aluminosilicate was obtained.

Thereafter, calcination was carried out for 3 hours at 780° C., and thusa proton type crystalline aluminosilicate was obtained.

Subsequently, 120 g of the proton type crystalline aluminosilicate thusobtained was impregnated with 120 g of an aqueous solution of galliumnitrate such that 0.4 mass % (a value calculated relative to 100 mass %of the total mass of the crystalline aluminosilicate) of gallium wouldbe supported, and the resultant was dried at 120° C. Thereafter, theproduct was calcined at 780° C. for 3 hours under an air stream, andthus a gallium-supported crystalline aluminosilicate was obtained.

Subsequently, 30 g of the gallium-supported crystalline aluminosilicatethus obtained was impregnated with 30 g of an aqueous solution ofdiammonium hydrogen phosphate such that 0.7 mass % of phosphorus (avalue calculated relative to 100 mass % of the total mass of thecrystalline aluminosilicate) would be supported, and the resultant wasdried at 120° C. Thereafter, the product was calcined at 780° C. for 3hours under an air stream, and thus a catalyst A containing acrystalline aluminosilicate, gallium and phosphorus was obtained.

Meanwhile, when the production of monocyclic aromatic hydrocarbons iscarried out in a fluidized bed reaction mode, the catalyst A furthercontains a silica binder (the content of the silica binder is 60 mass %relative to the total mass of the catalyst) in addition to thecrystalline aluminosilicate, gallium and phosphorus.

Example 1

LCO as indicated in Table 1 (10 vol % distillation temperature: 224.5°C., 90 vol % distillation temperature: 349.5° C.), which was afeedstock, was brought into contact with the catalyst A (a catalystproduced by incorporating a silica binder to an MFI type zeolitesupporting 0.4 mass % of gallium and 0.7 mass % of phosphorus, in anamount of 60 mass % relative to the total mass of the catalyst) in afluidized bed reactor under the conditions of a reaction temperature of550° C., a reaction pressure of 0.1 MPaG, and a contact time of 30seconds, and was allowed to react therewith, and thus production ofmonocyclic aromatic hydrocarbons was carried out.

The reaction product oil thus obtained was analyzed by an FID gaschromatographic method, and the amount of impurities between durene(boiling point: 196° C.) and naphthalene (boiling point: 218° C.) was1.9 mass % relative to 100 of naphthalene. Furthermore, the amount ofimpurities between naphthalene and 2-methylnaphthalene (boiling point:241° C.) was 0.6 mass % relative to 100 of naphthalene, and 0.4 mass %relative to 100 of methylnaphthalene. Thus, it was found that there werevery few components having a boiling point close to that of naphthalene.

Subsequently, the reaction product oil thus obtained was fractionated ina rectifying column into a gas fraction, a fraction containingmonocyclic aromatic hydrocarbons (benzene, toluene and xylene), and aheavy oil fraction having 9 or more carbon numbers (heavy oil fraction1).

The heavy oil fraction 1 was further distilled in the rectifying column,and was fractionated into a fraction mainly containing naphthalene(boiling point: 218° C.) and a fraction other than naphthalene (heavyoil fraction 2).

The yield of the monocyclic aromatic hydrocarbons (benzene, toluene, andcrude xylene (xylene including a small amount of ethylbenzene and thelike)) obtained by fractionation was 30 mass %, and the yield of thenaphthalene fraction was 7 mass %. Meanwhile, the naphthalene purity inthe naphthalene fraction was 96 mass %.

TABLE 1 Analysis Feedstock characteristics method Density @ 15° C. g/cm³0.906 JIS K 2249 Dynamic viscosity @ 30° C. mm²/s 3.640 JIS K 2283Distillate Initial boiling point ° C. 175.5 JIS K 2254 characteristics10 vol % distillation temperature ° C. 224.5 50 vol % distillationtemperature ° C. 274.0 90 vol % distillation temperature ° C. 349.5 Endpoint ° C. 376.0 Composition Saturated content vol % 35 JPI-5S-49analysis Olefin content vol % 8 Total aromatic content vol % 57Monocyclic aromatic content vol % 23 Bicyclic aromatic content vol % 25Tricyclic or higher-cyclic aromatic vol % 9 content

Example 2

LCO as indicated in Table 1 (10 vol % distillation temperature: 224.5°C., 90 vol % distillation temperature: 349.5° C.), which was afeedstock, was brought into contact with the catalyst A (an MFI typezeolite supporting 0.4 mass % of gallium and 0.7 mass % of phosphorus)in a fixed bed reactor under the conditions of a reaction temperature of550° C., a reaction pressure of 0.3 MPaG, and a contact time of 18seconds, and was allowed to react therewith, and thus production ofmonocyclic aromatic hydrocarbons was carried out.

The reaction product oil thus obtained was analyzed by an FID gaschromatographic method, and the amount of impurities between durene(boiling point: 196° C.) and naphthalene (boiling point: 218° C.) was2.4 mass % relative to 100 of naphthalene. Furthermore, the amount ofimpurities between naphthalene and 2-methylnaphthalene (boiling point:241° C.) was 1.6 mass % relative to 100 of naphthalene, and 0.9 mass %relative to 100 of methylnaphthalene. Thus, it was found that there werevery few components having a boiling point close to that of naphthalene.

Subsequently, the reaction product oil thus obtained was fractionated ina rectifying column into a gas fraction, a fraction containingmonocyclic aromatic hydrocarbons (benzene, toluene and crude xylene),and a heavy oil fraction having 9 or more carbon numbers.

The heavy oil fraction having 9 or more carbon numbers was furtherdistilled in the rectifying column, and was fractionated into a fractionmainly containing naphthalene (boiling point: 218° C.) and a fractionother than naphthalene.

The yield of the monocyclic aromatic hydrocarbons (benzene, toluene, andcrude xylene) obtained by fractionation was 37 mass %, and the yield ofthe naphthalene fraction was 9 mass %. Meanwhile, the naphthalene purityin the naphthalene fraction was 95 mass %.

Example 3

The fraction other than naphthalene (heavy oil fraction 2: content ofpolycyclic aromatic hydrocarbons is 95 mass % or more) obtained inExample 1 was subjected to a hydrogenation reaction by using acommercially available nickel-molybdenum catalyst under the conditionsof a reaction temperature of 350° C. and a reaction pressure of 5 MPaG.The hydrogenation reaction product thus obtained was 69 mass % ofhydrocarbon compounds having one aromatic ring, and 28 mass % ofcompounds having two or more aromatic rings (polycyclic aromatichydrocarbons). Thus, compared to the fraction before the hydrogenationreaction, the content of polycyclic aromatic hydrocarbons was reduced toa large extent.

Subsequently, a feedstock obtained by recycling the hydrogenationreaction product into the LCO indicated in Table 1 in an amount of 0.4times the mass of LCO, was brought into contact with the catalyst A (acatalyst produced by incorporating a silica binder to an MFI typezeolite supporting 0.4 mass % of gallium and 0.7 mass % of phosphorus,in an amount of 60 mass % relative to the total mass of the catalyst) ina fluidized bed reactor under the conditions of a reaction temperatureof 550° C., a reaction pressure of 0.3 MPaG, and a contact time of 30seconds, and was allowed to react therewith, and thus production ofmonocyclic aromatic hydrocarbons was carried out.

The yield of monocyclic aromatic hydrocarbons (benzene, toluene andcrude xylene) thus obtained was 36 mass %, and as compared with Example1 in which the hydrogenation reaction product was not recycled, anincrease in the yield of monocyclic aromatic hydrocarbons was observed.

From the results of Examples 1 to 3, it was found that according to themethod for producing aromatic hydrocarbons related to the invention,monocyclic aromatic hydrocarbons having 6 to 8 carbon numbers includingbenzene, toluene and crude xylene are obtained with high yield, andnaphthalene of high purity (90 mass % or higher) can be produced.

INDUSTRIAL APPLICABILITY

According to the method for producing aromatic hydrocarbons of thepresent invention, not only monocyclic aromatic hydrocarbons having 6 to8 carbon numbers but also naphthalene compounds including naphthalenecan all be produced by using an oil containing polycyclic aromatichydrocarbons such as LCO.

1. A method for producing aromatic hydrocarbons, the method comprisingthe steps of: bringing a feedstock having a 10 vol % distillationtemperature of 140° C. or higher and a 90 vol % distillation temperatureof 380° C. or lower, into contact with a catalyst for monocyclicaromatic hydrocarbon production containing a crystalline aluminosilicateto cause the feedstock to react with the catalyst, and thereby obtaininga product including monocyclic aromatic hydrocarbons having 6 to 8carbon numbers and a heavy oil fraction having 9 or more carbon numbers;separating respectively the monocyclic aromatic hydrocarbons having 6 to8 carbon numbers and the heavy oil fraction having 9 or more carbonnumbers from the product obtained from the cracking reforming reactionstep; purifying the monocyclic aromatic hydrocarbons having 6 to 8carbon numbers thus separated in the separation step, and collecting themonocyclic aromatic hydrocarbons having 6 to 8 carbon numbers; andseparating naphthalene compounds that include at least naphthalene, fromthe heavy oil fraction having 9 or more carbon numbers thus separated inthe separation step, and collecting the naphthalene compounds.
 2. Themethod for producing aromatic hydrocarbons according to claim 1, whereinthe step of collecting naphthalene is a process of separating andcollecting methylnaphthalene and/or dimethylnaphthalene, andnaphthalene.
 3. The method for producing aromatic hydrocarbons accordingto claim 1, further comprising the steps of: hydrogenating a remainingfraction obtained by separating naphthalene compounds in the step ofcollecting naphthalene, and obtaining a hydrogenation reaction product;and recycling the hydrogenation reaction product to the step of crackingreforming reaction.
 4. The method for producing aromatic hydrocarbonsaccording to claim 1, wherein in the step of collecting naphthalene, theapparatus for separating and collecting naphthalene compounds includingnaphthalene is a distillation apparatus.
 5. The method for producingaromatic hydrocarbons according to claim 1, wherein the crystallinealuminosilicate comprises a zeolite with medium-sized pores and/or azeolite with large-sized pores as main components.
 6. The method forproducing aromatic hydrocarbons according to claim 1, wherein thereaction temperature employed when the feedstock is allowed to reactwith the catalyst for monocyclic aromatic hydrocarbon production in thestep of cracking reforming reaction is from 400° C. to 650° C.
 7. Themethod for producing aromatic hydrocarbons according to claim 1, whereinthe reaction pressure employed when the feedstock is allowed to reactwith the catalyst for monocyclic aromatic hydrocarbon production in thestep of cracking reforming reaction is from 0.1 MPaG to 1.5 MPaG.
 8. Themethod for producing aromatic hydrocarbons according to claim 1, whereinthe contact time for bringing the feedstock into contact with thecatalyst for monocyclic aromatic hydrocarbon production in the step ofcracking reforming reaction is from 1 second to 300 seconds.